The 78-year-old was found by gardai in the city centre at around noon on Monday.

A hospital spokesman said the patient appeared to be well and was returned to the care of the hospital for a medical examination.

"The patient's family has been kept up to date and St James's wishes to publicly apologise to the patient and her family for this regrettable incident," he said.

"The hospital would like to thank the gardai and the public for their assistance."

The pensioner, a hospital patient since February, was in a 24-hour secure ward when she disappeared.

A spokesman said the hospital internal inquiry has not yet established how she walked out of the ward.

While she may have left with another patient's visitors, it is likely that this will not be fully established, he added.

He said: "In light of this incident the hospital is reviewing all of its patient care security arrangements, including reminding staff of the need for vigilance at all times, a review of access arrangements on all ward areas, the installation of more CCTV cameras and a review of existing cameras throughout the campus."